This invention relates to bicycle frames, and more particularly to the manufacture of bicycle frames from tubular frame components made from non-metallic materials.
The advantages of using high strength to weight composite materials, such as fiber-reinforced resin materials, as the major components of bicycle frames are well known in the industry, particularly for the purpose of reducing the overall weight of the frame. One such material made in tubular form from layers of fabric sheets impregnated with resin which has been found suitable in the manufacture of bicycle frames is disclosed in Foret U.S. Pat. No. 4,657,795 of 1987.
It has also been proposed in the bicycle industry to produce frames wherein tubular frame components are secured together by means of lugs formed of a different material. For example, Toyomasu U.S. Pat. No. 4,145,068 of 1969 discloses a bicycle frame comprising steel tubes which are connected together at their ends by lugs that are die-cast of aluminum bronze around the tube ends to be connected. Similarly, Grunfeld U.S. Pat. No. 3,541,649 of 1985 shows a frame construction wherein steel, aluminum or plastic tubular components are secured together by plastic lugs which are injection molded around the tube ends to be connected.
Such prior art structural expedients, however, have proved to be unacceptable in the manufacture of bicycle frames from fiber reinforced resin tube components, hereinafter referred to generally as "composite" materials. Not only do they produce high bonding stresses which result in weak joints, but these joints may further weaken and break due to differences in the rates of thermal expansion and contraction between the tube members and the lugs. In addition, many joints formed by the bonding of dissimilar materials tend to deteriorate as the result of galvanic corrosion.